whats yalls take on an "interference fit" shaft and joint?

[scottycoyote]

I play with an old schon, which is of course the 5/16 14 metal joint and piloted shafts. Both shafts have what im told is called an interference fit, meaning they screw down until the insert in the shaft touches the joint, and then the last turn or so is very very tight. I have another shaft i bought that doesnt fit like that, and is it just me or would that make it feel different? For some reason the schon just feels perfect (with the original shafts), but it doesnt feel the same with the other shaft. Does the interference fit really matter or make any difference in a way a stick hits, or once the sticks screwed together its basically together as long as everything fits true and flush and this is all in my head.

 

[Canadian cue]

Imo how tight the joint fits has a big effect on harmonics and feedback. The more surface area which is in intimate contact with each other the better the vibes will be transmitted to the bottom of the cue. Some makers achieve this with a big pin others use the pilot. The key to achieving the intimacy is by having one half the joint soft the other hard so as the one side can conform to the other giving you that interference fit.( It kind of parallels something else in life)

 

[Trueheart]

I play with an old schon, which is of course the 5/16 14 metal joint and piloted shafts. Both shafts have what im told is called an interference fit, meaning they screw down until the insert in the shaft touches the joint, and then the last turn or so is very very tight. I have another shaft i bought that doesnt fit like that, and is it just me or would that make it feel different? For some reason the schon just feels perfect (with the original shafts), but it doesnt feel the same with the other shaft. Does the interference fit really matter or make any difference in a way a stick hits, or once the sticks screwed together its basically together as long as everything fits true and flush and this is all in my head.

Interference Fit is a machinist term which means the pin is slightly larger than the hole, for a metal cue joint about .0001 inches. For metal pin into a wood hole about about .003 inches. For ease of assembly a slight taper is used to achieve this effect. An interference fit screw will not come loose in play and transmit feel better. Because of tight tolerances hard to do and affected greatly by wear or damage.

Trueheart

 

[scottycoyote]

Interference Fit is a machinist term which means the pin is slightly larger than the hole, for a metal cue joint about .0001 inches. For metal pin into a wood hole about about .003 inches. For ease of assembly a slight taper is used to achieve this effect. An interference fit screw will not come loose in play and transmit feel better. Because of tight tolerances hard to do and affected greatly by wear or damage.

Trueheart

is it the pin thats larger? I thought it was the rounded part of the insert in the shaft that causes the tightening effect and feel?

 

[Arnot Wadsworth]

Interference Fit is a machinist term which means the pin is slightly larger than the hole, for a metal cue joint about .0001 inches. For metal pin into a wood hole about about .003 inches. For ease of assembly a slight taper is used to achieve this effect. An interference fit screw will not come loose in play and transmit feel better. Because of tight tolerances hard to do and affected greatly by wear or damage.

Trueheart

I think that you will find that if the pin is larger than the hole the pin will not fit into the hole unless you heat the hole or use dry ice to shrink the pin. Depending on the material you might achieve a "press" fit but that won't apply with a cue because the cue would break before you achieved the fit. The hole must be larger than the pin to make any connection with a cue.

The fit I see most of the time is the piloted joint (5/16-14) whereas the brass pilot fits snugly into the hole. The more the cue is assembled and disassembled the less snug everything fits because the brass is soft and shows wear over time.

With the accuracy the brass inserts are made today it is not necessary to locate the pin with a pilot.

Just my opinion.

 

[MVPCues]

With the accuracy the brass inserts are made today it is not necessary to locate the pin with a pilot.

Just my opinion.

So the inside and outside threads of the inserts are much more concentric these days than I hear they sometimes are/have been? I have heard everything from you have to make your own... to true up the outside threads ...to press fit in the shaft ...to just rely on the inside threads be true to the pilot face etc etc.

The reason I thought the shaft insert was brass was it kept seizing from happening?
Kelly

 

[Cue Crazy]

The reason I thought the shaft insert was brass was it kept seizing from happening?
Kelly[/QUOTE]


Kelly, I think brass is actually easier on the oppossing threads of the pin then some other harder materials may be, therefore wears on the pin less. Not sure how much that has to do with It, but alot of times brass is used in high wear situations like the lead screw nuts on a crosslide for example. The brass does wear over time, but should'nt wear on the pin as much as if say the insert is made from SS. Also possible that there is less friction with the brass, but there are many machinists on here, perhaps one of them may have a better Idea then I since the subject seems kind of universal and maybe more in their area.
I have no idea myself about the locking, but have seen quick releases with brass inserts lock, but maybe that could be considered a different situation, since the design is different, and It might make sense that less friction should reduce the odds.

Another option to snug the joint at the bottom in a case where a pilot is used anyhow, Might be to ever so slightly taper the male pilot, so it snugs at the bottom.


Greg

 

[rhncue]

Threaded connecters, be it nuts and bolts, bolts screwed into threaded plates nor pins and inserts are used for alignment. They are only to hold things together. If you want something held together in perfect or repeatable alignment then there has to be a registry. On machinery there usually are pins that align, on piloted shafts the pilot is supposed to align although often it is only there for looks. Flat faced joints with inserts usually have no alignment and the only alignment is the friction between the threads in the pin and insert. There are now some pin/insert combinations that have a register on the pin. Radial pins have a register on the front of the pin when they are correctly installed.

Any time there is no registry there is no guarantee the shaft goes on to the butt aligned correctly.

Dick

 

[Canadian cue]

So the inside and outside threads of the inserts are much more concentric these days than I hear they sometimes are/have been? I have heard everything from you have to make your own... to true up the outside threads ...to press fit in the shaft ...to just rely on the inside threads be true to the pilot face etc etc.

The insert can be absolutely perfect but if the fit between the pin and insert is not a very close fit you still wont achieve concentricity.

The reason I thought the shaft insert was brass was it kept seizing from happening?
Kelly

There definitely is truth to this statement, if both pin and insert were of the same material and the same hardness the parts would have a very good chance of picking up on each other and causing it to lock up.

 

[Canadian cue]

Threaded connecters, be it nuts and bolts, bolts screwed into threaded plates nor pins and inserts are used for alignment. They are only to hold things together. If you want something held together in perfect or repeatable alignment then there has to be a registry. On machinery there usually are pins that align, on piloted shafts the pilot is supposed to align although often it is only there for looks. Flat faced joints with inserts usually have no alignment and the only alignment is the friction between the threads in the pin and insert. There are now some pin/insert combinations that have a register on the pin. Radial pins have a register on the front of the pin when they are correctly installed.

Any time there is no registry there is no guarantee the shaft goes on to the butt aligned correctly.

Dick

TAP,TAP,TAP

 

[Cue Crazy]

There are now some pin/insert combinations that have a register on the pin.

Dick[/QUOTE]


I thought of something like that one time, altough must admitt I was probably influenced by the way the radial is installed. Kind of a reversal of that. I recently ran accross some patents online, and saw It's nothing new, that It had already been done. Oh Well I like the Idea behind it though, would love to try one.

Greg